The simplest b2+ ion: Determining its structure from its energetics by a direct comparison of the threshold collision-induced dissociation of protonated oxazolone and diketopiperazine
The simplest b2+ ion: Determining its structure from its energetics by a direct comparison of the threshold collision-induced dissociation of protonated oxazolone and diketopiperazine
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DOI：
10.1016/j.ijms.2012.01.004
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发表时间：
2012-04-15
影响因子：
1.8
通讯作者：
Clark, Amy A.
中科院分区：
文献类型：
--
作者：
Armentrout, P. B.;Clark, Amy A.
比较了质子化GGG和GAG与质子化二酮哌嗪（H+DKP）的B（2）（+）离子的能量分辨碰撞诱导解离。使用引导离子束串联质谱仪获得绝对解离截面，并使用统计方法进行分析。来自H（+）GGG的B（2）（+）离子的碎裂模式与H+DKP的碎裂模式显著不同，尽管脱羰基（形成a（2）（+）离子）是发现的两种物质的最低能量途径。测得的B（2）（+）脱羰的阈值与H+DKP的阈值明显不同，但两个过程的起始点与量子化学计算所得的起始点一致，确定B（2）（+）离子为质子化的2-氨甲基-5-恶唑酮，H（+）AMOx。源自H（+）GAG的B（2）（+）离子的阈值略低，再次与理论一致。对所观察到的较高能量解离途径的检查表明，这些途径通常涉及初级a（2）（+）产物离子的后续解离。因此，这些途径的阈值信息的统计分析是困难的，并最终提供了与理论几乎没有协议。这种分歧是合理的基础上相当大的动能释放，已观察到的哈里森以前为这些后续反应。目前的结果也有利地与以前的结果相比，萧和同事，虽然一些改进的分析和机制的建议。(c)2012爱思唯尔有限公司版权所有。
Energy-resolved collision-induced dissociation of b(2)(+) ions derived from protonated GGG and GAG is compared with that of protonated diketopiperazine (H+DKP). Absolute dissociation cross sections are obtained using a guided ion beam tandem mass spectrometer and analyzed using statistical methods. The fragmentation pattern of the b(2)(+) ion from H(+)GGG differs significantly from that of H+DKP, although decarbonylation (forming the a(2)(+) ion) is the lowest energy pathway found for both species. The threshold measured for b(2)(+) decarbonylation differs appreciably from that of H+DKP, but both processes have onsets that are consistent with those obtained from quantum chemical calculations, positively identifying the b(2)(+) ion as the protonated 2-aminomethyl-5-oxazolone, H(+)AMOx. The threshold for the b(2)(+) ion derived from H(+)GAG has a slightly lower threshold, again consistent with theory. Examination of the higher energy dissociation pathways observed shows that these generally involve subsequent dissociation of the primary a(2)(+) product ion. As a consequence, statistical analysis of these pathways for threshold information is difficult and ultimately provides little agreement with theory. This disagreement is rationalized on the basis of considerable kinetic energy release that has been observed previously by Harrison for these subsequent reactions. The present results are also favorably compared with previous results obtained by Siu and coworkers, although a number of refinements in the analysis and mechanisms are suggested. (c) 2012 Elsevier B.V. All rights reserved.